Thanks for your question.
Do you have a copy of the guarantee agreement?
You should be entitled to a copy of the original loan agreement. They should provide a copy.
Was the original loan to a company? It may have been registered at companies house, if so you can obtain a copy of the original loan agreement from there.
If this was a business loan and depending on the amount it may be outside of the consumer credit act.
Have you spoken to the regulator / ombudsman about this.
I cannot find a conclusive answer.
I have been searching for the answer. I will opt out as one of the other experts may may know.